Resist composition and patterning process

ABSTRACT

Resist compositions comprising nitrogen heterocyclic compounds having a pyrrole or nitrogen-bearing 5-membered ring structure and a polar functional group have an excellent resolution and an excellent focus margin and are useful in microfabrication using electron beams or deep-UV light.

This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 2003-132790 filed in Japan on May 21, 2003, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a novel resist composition suitable for microfabrication technology, and more particularly to a chemical amplification resist composition. It also relates to a patterning process using the resist composition.

BACKGROUND ART

Of the efforts currently being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV lithography is capable of fabrication to dimensions of 0.2 μm or less and, when a resist having low light absorption is used, can form patterns with sidewalls that are nearly perpendicular to the substrate. One technology that has attracted a good deal of attention recently utilizes high-intensity KrF and ArF excimer lasers as the deep-UV light source. This technology is being used in large-volume production, prompting a desire for resists having a low light absorption and a high sensitivity.

Acid-catalyzed, positive-working chemical amplification resists (e.g., JP-B 2-27660 and JP-A 63-27829) developed in response to the above needs are endowed with excellent properties, including a high sensitivity, high resolution and good dry-etching resistance, which make them especially promising as resists for deep-UV lithography.

However, one problem with chemical amplification resists is that, when the standing time from exposure to post exposure bake (PEB) is long, the line pattern formed during patterning acquires a “T-top” shape characterized by widening at the top of the pattern. This defect is called “post exposure delay” (PED). Another problem with such resists is “footing,” which is a widening of the resist pattern close to the substrate that occurs on a basic substrate, particularly a silicon nitride or titanium nitride substrate. The T-top effect is believed to result from a decrease in solubility at the surface of the resist film, and the footing effect at the substrate surface appears to arise from a decline in solubility near the substrate. An additional problem is that lo acid-labile group elimination is a dark reaction which proceeds during the interval between the exposure step and the PEB step, reducing the final dimensions of the pattern lines.

These problems represent major drawbacks to the practical use of chemical amplification resists. Because of such defects, prior-art positive-working chemical amplification resists are difficult to dimensionally control in the lithographic process, and dimensional control is also lost during dry etching of the substrate (see, for example, W. Hinsberg et al., Journal of Photopolymer Science and Technology, Vol. 6, No. 4, 535–546 (1993); and T. Kumada et al., ibid., 571–574).

In positive-working chemical amplification resists, the problems of PED and footing on the substrate surface are believed to be caused in large part by basic compounds which are either airborne or present on the surface of the substrate. The acid at the surface of the resist film that has been generated by exposure reacts with airborne bases and is deactivated. Prolonged standing until post-exposure bake results in a corresponding increase in the amount of deactivated acid, making it more difficult for the acid-labile groups to decompose. A substantially insolubilized layer thus forms at the surface, giving the resist pattern a T-top shape.

It is well-known in the art that the addition of a basic compound can check the influence of airborne bases, and is thus effective also against PED (see, for example, JP-A 5-232706, JP-A 5-249683, JP-A 5-158239, JP-A 5-249662, JP-A 5-257282, JP-A 5-289322, JP-A 5-289340, JP-A 6-194834, JP-A 6-242605, JP-A 6-242606, JP-A 6-263716, JP-A 6-263717, JP-A 6-266100, JP-A 6-266111, JP-A 7-128859, JP-A 7-92678, JP-A 7-92680, JP-A 7-92681, JP-A 7-120929 and JP-A 7-134419).

Familiar basic compounds include nitrogenous compounds such as amine compounds and amide compounds. Specific examples include pyridine, polyvinylpyridine, aniline, N-methylaniline, N,N-dimethylaniline, o-toluidine, m-toluidine, p-toluidine, 2,4-lutidine, quinoline, isoquinoline, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, imidazole, α-picoline, β-picoline, γ-picoline, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2-quinolinecarboxylic acid, 2-amino-4-nitrophenol, and triazine compounds such as 2-(p-chlorophenyl)-4,6-trichloromethyl-S-triazine.

Of these, pyrrolidone, N-methylpyrrolidone, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid and 1,2-phenylenediamine are preferred.

These nitrogenous compounds are weak bases and can alleviate the T-top problem, but such compounds are unable to control the reaction when highly reactive acid-labile groups are used; that is, they cannot control acid diffusion. With the addition of a weak base, the dark reactions in PED in particular proceed in unexposed areas, causing slimming of the line dimensions and a loss of film thickness from the line surface during PED. To overcome such problems, it is desirable to add a strong base. However, a higher basicity is not necessarily better. For example, good effects cannot be obtained with the addition of the following super-strong bases: DBU (1,8-diazabicyclo[5.4.0]-7-undecene), DBN (1,5-diazabicyclo[4.3.0]-5-nonene), 1,8-bis(dimethylamino)naphthalene or quaternary ammonium hydroxides such as tetramethylammonium hydroxide.

The addition of a base having an excellent generated acid capturing effect works well to increase the contrast and thereby achieve a high resolution. The dissociation constants of the acid and base within water can be explained in terms of pKa, but the acid capturing-ability within the resist film is not directly related to the pKa of the base. This is discussed by Hatakeyama et al. in Journal of Photopolymer Science and Technology, Vol. 13, No. 4, pp. 519–524 (2000).

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a resist composition which has a high resist film thickness loss preventing effect, and also has a high resolution and a good focus margin widening effect. Another object of the invention is to provide a patterning method which uses such a resist.

The inventor has found that nitrogen heterocyclic compounds of general formula (1) or (2) below which bear polar functional groups such as carbonyl, ester, ether, sulfide, carbonate, cyano or acetal and have a pyrrole or other nitrogen heterocyclic structure can be prepared easily and in a high yield by the methods described later. When added in an appropriate amount to a resist, these compounds are highly effective for preventing a loss of resist film thickness and endow the resist composition with a high resolution and a focus margin widening effect.

Accordingly, the present invention provides a resist composition comprising at least one polar functional group-bearing nitrogen heterocyclic compound of the general formula (1) or (2) below.

Herein, A is a nitrogen atom or ≡C—R⁷; B is a nitrogen atom or ≡C—R⁸; R¹ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar function group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or a pair of R² and R³ and a pair of R⁴ and R⁵ may bond together to form a benzene, naphthalene or pyridine ring with the carbon atoms to which they are bonded; R⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms; R⁷ and R⁸ are each a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or R⁶ and R⁸ may bond together to form a benzene or naphthalene ring with the carbon atoms to which they are bonded.

One embodiment is a positive-working resist composition comprising (A) the nitrogen heterocyclic compound of formula (1) or (2), (B) an organic solvent, (C) a base resin having an acid labile group-protected acidic functional group which is alkali-insoluble or substantially alkali-insoluble, but becomes alkali-soluble when the acid-labile group is eliminated, (D) a photoacid generator, and optionally (E) a dissolution inhibitor.

Another embodiment is a negative-working resist comprising (A) the nitrogen heterocyclic compound of formula (1) or (2), (B) an organic solvent, (C′) a base resin which is alkali-soluble, but becomes substantially alkali-insoluble when crosslinked with a crosslinking agent, (D) a photoacid generator, and (F) a crosslinking agent which induces crosslinkage under the action of an acid.

The present invention provides as well a patterning process comprising the steps of (1) applying the resist composition onto a substrate; (2) heat treating the applied resist, then exposing the heat-treated resist through a photomask to high-energy radiation having a wavelength of at most 300 nm or an electron beam; and (3) heat treating the exposed resist, then developing the resist with a liquid developer.

DETAILED DESCRIPTION OF THE INVENTION

The nitrogen heterocyclic compound included in the inventive resist bears a polar functional group of formula (1) or (2) below.

In the formulas, A is a nitrogen atom or ≡C—R⁷, and B is a nitrogen atom or ≡C—R⁸. R¹ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar function group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups. R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms. Alternatively, a pair of R² and R³ and a pair of R⁴ and R⁵ may bond together to form a benzene ring, naphthalene ring or pyridine ring with the carbon atoms to which they are bonded. R⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms. R⁷ and R⁸ are each a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms. Alternatively, R⁶ and R⁸ may bond together to form a benzene ring or a naphthalene ring with the carbon atoms with which they are bonded.

In general formulas (1) and (2), the straight, branched or cyclic alkyl group having 2 to 20 carbon atoms, and preferably 2 to 10 carbon atoms, represented by R¹, bears at least one polar functional group selected from among hydroxyl, carbonyl, ether, ester, carbonate, sulfide, cyano and acetal groups. Specific, non-limiting examples of such alkyl groups include 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl, 2,3-dihydroxypropyl, 2-hydroxycylohexyl, 2-methoxyethyl, 2-ethoxyethyl, 2-(methoxymethoxy)ethyl, 2-(2-methoxyethoxy)ethyl, 2-[(2-methoxyethoxy)methoxy]ethyl, 2-[2-(2-methoxyethoxy)ethoxy]ethyl, 2-methoxymethoxypropyl, 2,3-bis(methoxymethoxy)propyl, tetrahydrofurfuryl, 2-tetrahydrofuryl, tetrahydro-2H-pyran-2-yl, tetrahydro-2H-pyran-4-yl, 2-(tetrahydro-2H-pyran-2-yloxy)ethyl, 2,2-dimethoxyethyl, 3,3-diethoxypropyl, 1,3-dioxolan-2-ylmethyl, 1,3-dioxolan-4-ylmethyl, 2,2-dimethyl-1,3-dioxolan-4-ylmethyl, 2-formyloxyethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 2-valeryloxyethyl, 2-hexanoyloxyethyl, 2-(cyclohexanecarbonyloxy)ethyl, 2-(tetrahydrofuran-2-carbonyloxy)ethyl, 2-methoxyacetoxyethyl, 2-[(2-methoxyethoxy)acetoxy]ethyl, 3-acetoxypropyl, 2-acetoxypropyl, 4-acetoxybutyl, 2,3-diacetoxypropyl, 2-methoxycarbonyloxy, 2-t-butoxycarbonyloxy, (2-oxo-1,3-dioxolan-4-yl)methyl, 2-oxotetrahydrofuran-3-yl, 5-oxotetrahydrofuran-3-yl, 2-oxotetrahydro-2H-pyran-3-yl, 2-(2-acetoxyethoxy)ethyl, methoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl, 4-(methoxycarbonyl)butyl, ethoxycarbonylmethyl, 2-(ethoxycarbonyl)ethyl, 3-(ethoxycarbonyl)propyl, 4-(ethoxycarbonyl)butyl, 3,3-bis(methoxycarbonyl)propyl, 2-oxopropyl, 2-tetrahydrothienyl, 2-tetrahydrotenyl, 2-(methylthiomethoxy)ethyl, cyanomethyl, 2-cyanoethyl, 3-cyanopropyl, 4-cyanobutyl and 3,3-dicyanopropyl groups.

Specific, non-limiting, examples of the straight, branched or cyclic alkyl groups having 1 to 10 carbon atoms and the aryl groups having 6 to 10 carbon atoms represented by R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ in general formulas (1) and (2) and in A and B include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, decyl, cyclopentyl, cyclohexyl, phenyl, tolyl, xylyl and naphthyl.

Specific examples of the nitrogen heterocyclic compounds having a pyrrole skeleton and a polar functional group which are represented by formula (1) include, but are not limited to, the following. In the structural formulas that appear below, “Me” represents methyl, “Et” represents ethyl, “t-Bu” represents t-butyl, “Ac” represents acetyl and “Ph” represents phenyl.

Specific examples of the nitrogen heterocyclic compounds having a polar functional group which are represented by formula (2) include, but are not limited to, the following.

According to the invention, the nitrogen heterocyclic compounds have a pyrrole, azole or other suitable partial structure and pendant polar functional groups within the molecule. The polar functional groups having a high kinetic affinity to acids can be placed at suitable positions near the nitrogens that ultimately capture the acid. As a result, generated acids can be rapidly captured, enabling photoresists containing these basic compounds to achieve a high resolution and a wide focus margin. By selecting an optimal combination from among the possible combinations of A and B and R¹ to R⁸ in formulas (1) and (2), the basicity, acid capturing rate and diffusion rate within the resist can be suitably adjusted. Therefore, the nitrogen heterocyclic compound additives are compatible with a broad range of resist polymers and photoacid generators.

The inventive resist composition is most preferably either a positive-working chemical amplification resist composition which includes:

(A) the above-described nitrogen heterocyclic compound,

(B) an organic solvent,

(C) a base resin having an acid labile group-protected acidic functional group, which is alkali-insoluble or substantially alkali-insoluble, but becomes alkali-soluble when the acid labile group is eliminated,

(D) a photoacid generator and, optionally,

(E) a dissolution inhibitor; or a negative-working chemical amplification resist composition which includes:

(A) the above-described nitrogen heterocyclic compound,

(B) an organic solvent,

(C′) a base resin which is alkali-soluble, but becomes substantially alkali-insoluble when crosslinked with a crosslinking agent (F),

(D) a photoacid generator, and

(F) a crosslinking agent which induces crosslinkage under the action of an acid.

These components are described in detail.

(B) Organic Solvent

The organic solvent used herein may be any organic solvent in which the base resin, photoacid generator, and other components are soluble. Illustrative, non-limiting, examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amylketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as γ-butyrolactone. These solvents may be used alone or in combinations of two or more thereof. Of the above organic solvents, it is recommended to use diethylene glycol dimethyl ether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, cyclohexanone and mixtures thereof because the photoacid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000 parts, especially about 400 to 2,000 parts by weight per 100 parts by weight of the base resin.

(C) Base Polymer

The base polymers used as component (C) or (C′) in the inventive compositions include polyhydroxystyrene (PHS), and copolymers of PHS with styrene, (meth)acrylic acid esters or other polymerizable olefinic compounds, for KrF excimer laser resist use; (meth)acrylic acid ester polymers, alternating copolymers of cycloolefin with maleic anhydride, copolymers containing vinyl ethers or (meth)acrylic acid esters, polynorbornene, and ring-opening metathesis polymerized cycloolefins, for ArF excimer laser resist use; and fluorinated forms of the foregoing polymers (for both KrF and ArF laser uses) for F₂ excimer laser resist use. The base polymers may be used alone or in admixture of two or more. In the case of positive resist compositions, it is a common practice to substitute acid labile groups for hydroxyl groups on phenol, carboxyl groups or fluorinated alkyl alcohols for reducing the rate of dissolution in unexposed regions.

The acid labile groups to be introduced into the base polymers may be selected from a variety of such groups, preferably from acetal groups of 2 to 30 carbon atoms and tertiary alkyl groups of 4 to 30 carbon atoms having the formulae (C1) and (C2), respectively.

In formulae (C1) and (C2), R¹ and R² each are hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, which may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine, R³, R⁴, R⁵ and R⁶ each are a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, an aryl group or an aralkyl group, which may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine. A pair of R¹ and R², a pair of R¹ and R³, a pair of R² and R³, a pair of R⁴ and R⁵, a pair of R⁴ and R⁶, or a pair of R⁵ and R⁶, taken together, may form a ring with the carbon atom to which they are attached.

Illustrative examples of the acetal group of formula (C1) include, but are not limited to, methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, isopropoxymethyl, t-butoxymethyl, 1-methoxyethyl, 1-methoxypropyl, 1-methoxybutyl, 1-ethoxyethyl, 1-ethoxypropyl, 1-ethoxybutyl, 1-propoxyethyl, 1-propoxypropyl, 1-propoxybutyl, 1-cyclopentyloxyethyl, 1-cyclohexyloxyethyl, 2-methoxyisopropyl, 2-ethoxyisopropyl, 1-phenoxyethyl, 1-benzyloxyethyl, 1-phenoxypropyl, 1-benzyloxypropyl, 1-adamantyloxyethyl, 1-adamantyloxypropyl, 2-tetrahydrofuryl, 2-tetrahydro-2H-pyranyl, 1-(2-cyclohexanecarbonyloxyethoxy)ethyl, 1-(2-cyclohexanecarbonyloxyethoxy)propyl, 1-[2-(1-adamantylcarbonyloxy)ethoxy]ethyl, and 1-[2-(1-adamantylcarbonyloxy)ethoxy]propyl.

Illustrative examples of the tertiary alkyl group of formula (C2) include, but are not limited to, t-butyl, t-pentyl, 1-ethyl-1-methylpropyl, 1,1-diethylpropyl, 1,1,2-trimethylpropyl, 1-adamantyl-1-methylethyl, 1-methyl-1-(2-norbornyl)ethyl, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl, 1-methyl-1-(7-oxanorbornan-2-yl)ethyl, 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-propylcyclopentyl, 1-cyclopentylcyclopentyl, 1-cyclohexylcyclopentyl, 1-(2-tetrahydrofuryl)cyclopentyl, 1-(7-oxanorbornan-2-yl)cyclopentyl, 1-methylcyclohexyl, 1-ethylcyclohexyl, 1-cyclopentylcyclohexyl, 1-cyclohexylcyclohexyl, 2-methyl-2-norbornyl, 2-ethyl-2-norbornyl, 8-methyl-8-tricyclo[5.2.1.0^(2,6)]decyl, 8-ethyl-8-tricyclo[5.2.1.0^(2,6)]decyl, 3-methyl-3-tetracyclo[4.4.0.1^(2,5).1 ^(7,10)]dodecyl, 3-ethyl-3-tetracyclo[4.4.0.1^(2,5).1 ^(7,10)]dodecyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1-methyl-3-oxo-1-cyclohexyl, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl, 5-hydroxy-2-methyl-2-adamantyl, and 5-hydroxy-2-ethyl-2-adamantyl.

In the base resin, at least 1 mol % of hydrogen atoms of hydroxyl groups may be substituted with acid labile groups of the following general formula (C3a) or (C3b) for crosslinkage between molecules or within a molecule.

Herein, R⁷ and R⁸ each are hydrogen or a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, or R⁷ and R⁸, taken together, may form a ring, with the proviso that each of R⁷ and R⁸ is a straight or branched alkylene group of 1 to 8 carbon atoms when they form a ring. R⁹ is a straight, branched or cyclic alkylene group of 1 to 10 carbon atoms. Letter “a” is an integer of 1 to 7 and “b” is 0 or an integer of 1 to 10. “A” is a (a+1)-valent aliphatic or alicyclic saturated hydrocarbon group, aromatic hydrocarbon group or heterocyclic group of 1 to 50 carbon atoms, which may have an intervening hetero atom and in which the hydrogen atom attached to a carbon atom may be partially replaced by a hydroxyl group, carboxyl group, carbonyl group or fluorine atom. B is —CO—O—, —NHCO—O— or —NHCONH—.

Illustrative examples of the crosslinking acetal linkages represented by formulae (C3a) and (C3b) are given below as (C3)-1 through (C3)-8, but not limited thereto.

Preferably the base polymer has a weight average molecular weight of 2,000 to 100,000. With Mw below 2,000, film formation and resolution may become poor. With Mw beyond 100,000, resolution may become poor or foreign matter may generate during pattern formation.

(D) Photoacid Generator

The photoacid generator is a compound capable of generating an acid upon exposure to high energy radiation or electron beams and includes the following:

-   (i) onium salts of-the formula (P1a-1), (P1a-2) or (P1b), -   (ii) diazomethane derivatives of the formula (P2), -   (iii) glyoxime derivatives of the formula (P3), -   (iv) bissulfone derivatives of the formula (P4), -   (v) sulfonic acid esters of N-hydroxyimide compounds of the formula     (P5), -   (vi) β-ketosulfonic acid derivatives, -   (vii) disulfone derivatives, -   (viii) nitrobenzylsulfonate derivatives, -   (ix) sulfonate derivatives, and -   (x) oxime sulfonates.

These photoacid generators are described in detail.

(i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently represent straight, branched or cyclic alkyl, alkenyl or oxoalkyl groups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, or aralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some or all of the hydrogen atoms may be replaced by alkoxy or other groups. Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b) and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when they form a ring. K⁻ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and are illustrated below. Exemplary alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl. Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl, hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include 2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl, 2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and 2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyl and naphthyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, and m-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl, 4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such as methylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such as methoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such as dimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups such as dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groups include benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkyl groups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl, 2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples of the non-nucleophilic counter ion represented by K⁻ include halide ions such as chloride and bromide ions, fluoroalkylsulfonate ions such as triflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate, arylsulfonate ions such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, and alkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branched or cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents a straight, branched or cyclic alkylene groups of 1 to 10 carbon atoms. R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to 7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl. Illustrative of the groups represented by R¹⁰³ are methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, 1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene, 1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of the groups represented by R^(104a) and R^(104b) are 2-oxopropyl, 2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrative examples of the counter ion represented by K⁻ are the same as exemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane Derivatives of Formula (P2)

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of 7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl, cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkyl groups include trifluoromethyl, 1,1,1-trifluoroethyl, 1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups include phenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, and m-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl, 4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groups include fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl. Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime Derivatives of Formula (P3)

Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight, branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, may form a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branched alkylene groups of 1 to 6 carbon atoms when they form a ring.

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenated aryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are the same as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylene groups represented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene, butylene, and hexylene.

(iv) Bissulfone Derivatives of Formula (P4)

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic Acid Esters of N-Hydroxyimide Compounds of Formula (P5)

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene group of 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atoms wherein some or all of the hydrogen atoms may be replaced by straight or branched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl, or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl group wherein some or all of the hydrogen atoms may be replaced by alkyl or alkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may have substituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, or chlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include 1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups include methylene, ethylene, trimethylene, tetramethylene, phenylethylene, and norbornane-2,3-diyl; and exemplary alkenylene groups include 1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl. Of the groups represented by R¹¹¹, exemplary alkyl groups are as exemplified for R^(101a) to R^(101c); exemplary alkenyl groups include vinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl, 3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl, 1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplary alkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl, hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl, methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl, methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl and tert-butyl; and the alkoxy groups of 1 to 4 carbon atoms include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy. The phenyl groups which may have substituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group include phenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl. The hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl and furyl.

Illustrative examples of the photoacid generator include:

onium salts such as diphenyliodonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate, diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate, tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate, triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfonium butanesulfonate, trimethylsulfonium trifluoromethanesulfonate, trimethylsulfonium p-toluenesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate, dimethylphenylsulfonium trifluoromethanesulfonate, dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfonium trifluoromethanesulfonate, dicyclohexylphenylsulfonium p-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate, (2-norbornyl)methyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate, ethylenebis[methyl(2-oxocyclopentyl)sulfonium trifluoromethanesulfonate], and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as bis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(xylenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane, bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane, bis(tert-amylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane, 1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and 1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such as bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime, bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime, bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime, bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime, bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-O-(n-butanesulfonyl)-α-dimethylglyoxime, bis-O-(n-butanesulfonyl)-α-diphenylglyoxime, bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime, bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime, bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime, bis-O-(methanesulfonyl)-α-dimethylglyoxime, bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime, bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime, bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime, bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime, bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime, bis-O-(benzenesulfonyl)-α-dimethylglyoxime, bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime, bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime, bis-O-(xylenesulfonyl)-α-dimethylglyoxime, and bis-O-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as bisnaphthylsulfonylmethane, bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane, bisethylsulfonylmethane, bispropylsulfonylmethane, bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, and bisbenzenesulfonylmethane;

β-ketosulfone derivatives such as 2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and 2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzyl p-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as 1,2,3-tris(methanesulfonyloxy)benzene, 1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and 1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as N-hydroxysuccinimide methanesulfonate, N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide ethanesulfonate, N-hydroxysuccinimide 1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate, N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimide 1-octanesulfonate, N-hydroxysuccinimide p-toluenesulfonate, N-hydroxysuccinimide p-methoxybenzenesulfonate, N-hydroxysuccinimide 2-chloroethanesulfonate, N-hydroxysuccinimide benzenesulfonate, N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate, N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide 2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate, N-hydroxymaleimide methanesulfonate, N-hydroxymaleimide ethanesulfonate, N-hydroxy-2-phenylmaleimide methanesulfonate, N-hydroxyglutarimide methanesulfonate, N-hydroxyglutarimide benzenesulfonate, N-hydroxyphthalimide methanesulfonate, N-hydroxyphthalimide benzenesulfonate, N-hydroxyphthalimide trifluoromethanesulfonate, N-hydroxyphthalimide p-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, N-hydroxynaphthalimide benzenesulfonate, N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate, N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate, and N-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

Preferred among these photoacid generators are onium salts such as triphenylsulfonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate, triphenylsulfonium p-toluenesulfonate, (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate, tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate, cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate, (2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoromethanesulfonate, and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate; diazomethane derivatives such as bis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane, and bis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such as bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime and bis-O-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives such as bisnaphthylsulfonylmethane; and sulfonic acid esters of N-hydroxyimide compounds such as N-hydroxysuccinimide methanesulfonate, N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide 1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate, N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimide p-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, and N-hydroxynaphthalimide benzenesulfonate.

Also included are the oxime sulfonates described in U.S. Pat. No. 6,004,724, for example, (5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile, (5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile, (5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile, (5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile, (5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile, (5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile, etc.

Also included are the oxime sulfonates described in U.S. Pat. No. 6,261,738 and JP-A 2000-314956, for example,

-   2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-phenyl-ethanone     oxime-O-(4-methoxyphenylsulfonate); -   2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate); -   2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate); -   2,2,2-trifluoro-1-phenyl-ethanone     oxime-O-(2,4,6-trimethylphenylsulfonate); -   2,2,2-trifluoro-1-(4-methylphenyl)-ethanone     oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-(4-methylphenyl)-ethanone     oxime-O-(methylsulfonate); -   2,2,2-trifluoro-1-(2-methylphenyl)-ethanone     oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone     oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone     oxime-O-(1-naphthylsulfonate); -   2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone     oxime-O-(2-naphthylsulfonate); -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(1-naphthylsulfonate); -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(2-naphthylsulfonate); -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanone     oxime-O-(10-camphorylsulfonate); -   2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-10-camphorylsulfonate; -   2,2,2-trifluoro-1-(phenyl)-ethanone     oxime-O-(4-methoxyphenyl)sulfonate; -   2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(1-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(2-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(phenyl)-ethanone     oxime-O-(2,4,6-trimethylphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-methylphenyl)-ethanone     oxime-O-(10-camphoryl)sulfonate; -   2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(2-methylphenyl)-ethanone     oxime-O-(10-camphoryl)sulfonate; -   2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone     oxime-O-(1-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone     oxime-O-(2-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(10-camphoryl)sulfonate; -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(1-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone     oxime-O-(2-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone     oxime-O-(4-methylphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone     oxime-O-(4-methylphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone     oxime-O-(4-dodecylphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate; -   2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone     oxime-O-(4-methoxyphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone     oxime-O-(4-dodecylphenyl)sulfonate; -   2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone     oxime-O-octylsulfonate; -   2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone     oxime-O-(2-naphthyl)sulfonate; -   2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate; -   2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate; -   2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanone     oxime-O-(10-camphoryl)sulfonate; -   2,2,2-trifluoro-1-naphthyl-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-2-naphthyl-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-[4-benzylphenyl]-ethanone oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanone     oxime-O-methylsulfonate; -   2,2,2-trifluoro-1-naphthyl-ethanone oxime-O-propylsulfonate; -   2,2,2-trifluoro-2-naphthyl-ethanone oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-benzylphenyl]-ethanone oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanone     oxime-O-propylsulfonate; -   1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoroethanone     oxime-O-sulfonyl]phenyl; -   2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[4-benzyloxyphenyl]-ethanone     oxime-O-propylsulfonate; -   2,2,2-trifluoro-1-[2-thiophenyl]-ethanone oxime-O-propylsulfonate;     and -   2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanone     oxime-O-propylsulfonate.

Also included are the oxime sulfonates described in JP-A 9-95479 and JP-A 9-230588 and the references cited therein, for example,

-   α-(p-toluenesulfonyloxyimino)-phenylacetonitrile, -   α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile, -   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2-thienylacetonitrile, -   α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile, -   α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile, -   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]-acetonitrile, -   α-(tosyloxyimino)-3-thienylacetonitrile, -   α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, and -   α-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Suitable bisoxime sulfonates include those described in JP-A 9-208554, for example,

-   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,     etc.

These photoacid generators may be used singly or in combinations of two or more thereof. Onium salts are effective for improving rectangularity, while diazomethane derivatives and glyoxime derivatives are effective for reducing standing waves. The combination of an onium salt with a diazomethane or a glyoxime derivative allows for fine adjustment of the profile.

The photoacid generator is added in an amount of 0.1 to 50 parts, and especially 0.5 to 40 parts by weight, per 100 parts by weight of the base resin. Less than 0.1 part of the photoacid generator may generate a less amount of acid upon exposure, sometimes leading to a poor sensitivity and resolution whereas more than 50 parts of the photoacid generator may adversely affect the transmittance and resolution of resist.

(E) Dissolution Inhibitor

To the resist composition, a dissolution inhibitor may be added. The dissolution inhibitor is a compound having on the molecule at least two phenolic hydroxyl groups, in which an average of from 0 to 100 mol % of all the hydrogen atoms on the phenolic hydroxyl groups are replaced with acid labile groups or a compound having on the molecule at least one carboxyl group, in which an average of 50 to 100 mol % of all the hydrogen atoms on the carboxyl groups are replaced with acid labile groups, both the compounds having an average molecular weight within a range of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolic hydroxyl groups with acid labile groups is on average at least 0 mol %, and preferably at least 30 mol %, of all the phenolic hydroxyl groups. The upper limit is 100 mol %, and preferably 80 mol %. The degree of substitution of the hydrogen atoms on the carboxyl groups with acid labile groups is on average at least 50 mol %, and preferably at least 70 mol %, of all the carboxyl groups, with the upper limit being 100 mol %.

Preferable examples of such compounds having two or more phenolic hydroxyl groups or compounds having at least one carboxyl group include those of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight or branched alkyl or alkenyl of 1 to 8 carbon atoms; R²⁰³ is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or —(R²⁰⁷)_(h)—COOH; R²⁰⁴ is —(CH₂)_(i)— (where i=2 to 10), an arylene of 6 to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁵ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶ is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or a hydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straight or branched alkylene of 1 to 10 carbon atoms; R²⁰⁸ is hydrogen or hydroxyl; the letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has at least one hydroxyl group; and a is a number such that the compounds of formula (D8) or (D9) have a molecular weight of from 100 to 1,000.

The above compounds have a weight average molecular weight within a range of 100 to 1,000, and preferably 150 to 800.

The dissolution inhibitor may be formulated in an amount of 0 to 50 parts, preferably 5 to 50 parts, and more preferably 10 to 30 parts by weight, per 100 parts by weight of the base resin, and may be used singly or as a mixture of two or more thereof. Too less an amount of the dissolution inhibitor may fail to improve resolution whereas the use of more than 50 parts may lead to slimming of the patterned film, and thus a decline in resolution.

(F) Crosslinker

Formulated in the negative resist composition is a crosslinker (F) which forms a crosslinked structure under the action of acid. Typical crosslinkers are compounds having at least two hydroxymethyl, alkoxymethyl, epoxy or vinyl ether groups within a molecule. Substituted glycoluril derivatives, urea derivatives, and hexa(methoxymethyl)melamine compounds are suitable as the crosslinker. Examples include N,N,N′,N′-tetramethoxymethylurea, hexamethylmelamine, tetraalkoxymethyl-substituted glycoluril compounds such as tetrahydroxymethyl-substituted glycoluril and tetramethoxymethylglycoluril, and condensates of phenolic compounds such as substituted or unsubstituted bis(hydroxymethylphenol) compounds and bisphenol A with epichlorohydrin. Especially preferred crosslinkers are 1,3,5,7-tetraalkoxymethylglycolurils such as 1,3,5,7-tetramethoxymethylglycoluril, 1,3,5,7-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol, 2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A, 1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea, and hexamethoxymethylmelamine. In the resist composition, an appropriate amount of the crosslinker is, though not limited thereto, about 1 to 25 parts, and especially about 5 to 20 parts by weight per 100 parts by weight of the base resin in the composition. The crosslinkers may be used alone or in admixture of two or more.

In addition to the inventive nitrogen-containing heterocyclic compound, one or more of commonly used basic compounds may be employed in the inventive resist composition. Examples of suitable conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, carboxyl group-bearing nitrogenous compounds, sulfonyl group-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenous compounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholic nitrogenous compounds, amide derivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, and tetraethylenepentamine. Examples of suitable secondary aliphatic amines include dimethylamine, diethylamine, di-n-propylamine, di-iso-propylamine, di-n-butylamine, di-iso-butylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, and N,N-dimethyltetraethylenepentamine. Examples of suitable tertiary aliphatic amines include trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,N′,N′-tetramethylmethylenediamine, N,N,N′,N′-tetramethylethylenediamine, and N,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, and benzyldimethylamine. Examples of suitable aromatic and heterocyclic amines include aniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazole derivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g., thiazole and isothiazole), imidazole derivatives (e.g., imidazole, 4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives, pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives, imidazolidine derivatives, pyridine derivatives (e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridone, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives, piperidine derivatives, piperazine derivatives, morpholine derivatives, indole derivatives, isoindole derivatives, 1H-indazole derivatives, indoline derivatives, quinoline derivatives (e.g., quinoline and 3-quinolinecarbonitrile), isoquinoline derivatives, cinnoline derivatives, quinazoline derivatives, quinoxaline derivatives, phthalazine derivatives, purine derivatives, pteridine derivatives, carbazole derivatives, phenanthridine derivatives, acridine derivatives, phenazine derivatives, 1,10-phenanthroline derivatives, adenine derivatives, adenosine derivatives, guanine derivatives, guanosine derivatives, uracil derivatives, and uridine derivatives.

Examples of suitable carboxyl group-bearing nitrogenous compounds include aminobenzoic acid, indolecarboxylic acid, and amino acid derivatives (e.g. nicotinic acid, alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples of suitable sulfonyl group-bearing nitrogenous compounds include 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples of suitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenyl group-bearing nitrogenous compounds, and alcoholic nitrogenous compounds include 2-hydroxypyridine, aminocresol, 2,4-quinolinediol, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide. Examples of suitable amide derivatives include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, and benzamide. Suitable imide derivatives include phthalimide, succinimide, and maleimide.

In addition, basic compounds of the following general formula (B)-1 may also be included alone or in admixture. N(X)_(n)(Y)_(3-n)  (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain an ether or hydroxyl group; and side chain X is independently selected from groups of the following general formulas (X)-1 to (X)-3, and two or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight or branched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ are independently hydrogen, straight, branched or cyclic alkyl groups of 1 to 20 carbon atoms, which may contain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³ is a single bond or a straight or branched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, which may contain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the basic compounds of formula (B)-1 include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4, 1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine, N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine, tris(2-methoxycarbonyloxyethyl)amine, tris(2-tert-butoxycarbonyloxyethyl)amine, tris[2-(2-oxopropoxy)ethyl]amine, tris[2-(methoxycarbonylmethyl)oxyethyl]amine, tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine, tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine, tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine, N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine, N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine, N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine, N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine, N-methyl-bis(2-pivaloyloxyethyl)amine, N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine, N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine, tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine, N-butyl-bis(methoxycarbonylmethyl)amine, N-hexyl-bis(methoxycarbonylmethyl)amine, and β-(diethylamino)-δ-valerolactone.

Also useful are one or more of cyclic structure-bearing basic compounds having the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain one or more carbonyl, ether, ester or sulfide groups.

Illustrative examples of the cyclic structure-bearing basic compounds having formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine, 1-[2-(methoxymethoxy)ethyl]piperidine, 4-[2-(methoxymethoxy)ethyl]morpholine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine, 4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate, 2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethyl methoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine, 1-[2-(t-butoxycarbonyloxy)ethyl]piperidine, 4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl 3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl 3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl 2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate, methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl 3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate, 2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate, tetrahydrofurfuryl 3-morpholinopropionate, glycidyl 3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate, 2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl 3-morpholinopropionate, cyclohexyl 3-piperidinopropionate, α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methyl piperidinoacetate, methyl morpholinoacetate, methyl thiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, and 2-methoxyethyl morpholinoacetate.

Also, one or more of cyano-bearing basic compounds having the following general formulae (B)-3 to (B)-6 may be blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are each independently a straight or branched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the cyano-bearing basic compounds having formulae (B)-3 to (B)-6 include 3-(diethylamino)propiononitrile, N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile, N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile, N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile, N,N-bis(2-methoxyethyl)-3-aminopropiononitrile, N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate, N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile, N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile, N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile, N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile, N,N-bis(2-hydroxyethyl)aminoacetonitrile, N,N-bis(2-acetoxyethyl)aminoacetonitrile, N,N-bis(2-formyloxyethyl)aminoacetonitrile, N,N-bis(2-methoxyethyl)aminoacetonitrile, N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate, N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile, N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile, N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile, N-cyanomethyl-N-[2-(methoxymethoxy)ethyl]aminoacetonitrile, N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile, N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile, N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile, 1-piperidinepropiononitrile, 4-morpholinepropiononitrile, 1-pyrrolidineacetonitrile, 1-piperidineacetonitrile, 4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate, cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl 3-diethylaminopropionate, 2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl 1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl 4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate, 2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl 4-morpholinepropionate.

The conventional basic compounds may be used alone or in admixture of two or more. The conventional basic compound is preferably formulated in an amount of 0 to 2 parts, and especially 0 to 1 part by weight, per 100 parts by weight of the base resin.

In addition to the above components, the inventive resist composition may optionally include additives such as surfactants, acidic compounds, stabilizers and dyes.

Patterning with the inventive resist composition may be carried out by a conventional process. Such a process typically includes the steps of:

-   (1) applying the above-described chemical amplification resist     composition onto a substrate; -   (2) heat treating the applied resist, then exposing the heat-treated     resist through a photomask to high-energy radiation having a     wavelength of at most 300 nm, preferably at most 250 nm, or an     electron beam; and -   (3) heat treating the exposed resist, then developing the resist     with a liquid developer.

It is desirable for the nitrogen heterocyclic compound of the invention to be included in an amount of 0.001 to 2 parts by weight, and especially 0.01 to 1 part by weight, per 100 parts by weight of the overall base resin. The use of less than 0.001 part may have no perceivable effect, whereas the use of more than 2 parts may lower the sensitivity of the resist.

Preferably, the nitrogen heterocyclic compound of the invention having a pyrrole or other nitrogen-containing five-membered ring structure and a polar functional group, represented by formula (1) or (2), is prepared by a method which is selected optimal for the structure of the compound.

Specific, non-limiting, examples are methods that employ the following N-alkylation reactions between a nitrogen-containing 5-membered ring compound which is a secondary amine and an alkylating agent.

In the above formulas, A is a nitrogen atom or ≡C—R⁷; B is a nitrogen atom or ≡C—R⁸; R¹ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar function group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or a pair of R² and R³ and a pair of R⁴ and R⁵ may bond together to form a benzene, naphthalene or pyridine ring with the carbon atoms to which they are bonded; R⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms; R⁷ and R⁸ are each a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or R⁶ and R⁸ may bond together to form a benzene or naphthalene ring with the carbon atoms to which they are bonded. X is an eliminatable group such as a halogen atom, an alkylsulfonyloxy group or an arylsulfonoxy group.

In the above reactions, it is desirable to use the alkylating agent R¹X in an amount of 0.3 to 10 moles, and especially 0.5 to 2 moles, per mole of the secondary amine (3) or (4). The reaction may be carried out in a solvent or in the absence of a solvent. Solvents that may be selected in accordance with the reaction conditions and used, either singly or as mixtures thereof, include alcohols such as methanol, ethanol, isopropyl alcohol, t-butyl alcohol and ethylene glycol; hydrocarbons such as hexane, heptane, benzene, toluene and xylene; ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane and diglyme; chlorinated solvents such as methylene chloride, chloroform and 1,2-dichloroethylene; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone; carboxylic acids such as formic acid and acetic acid; esters such as ethyl acetate and butyl acetate; ketones such as acetone and 2-butanone; nitriles such as acetonitrile; amines such as pyridine and triethylamine; and water. The reaction temperature may be selected from a range of 0° C. to the reflux temperature of the solvent, in accordance with the reaction rate. The base used in the invention may be selected in accordance with the reaction conditions from among amines such as pyridine, triethylamine, diisopropylethylamine, 4-dimethylaminopyridine and imidazole; alkoxy metals such as sodium methoxide, sodium ethoxide and potassium t-butoxide; carbonates such as sodium carbonate, potassium carbonate and cesium carbonate; hydroxides such as sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide; metal hydrides such as sodium hydride and potassium hydride; organometallic compounds such as butyllithium and ethyl magnesium bromide; and metal amides such as lithium diisopropylamide. Any one or mixture of these bases may be used. It is desirable for the amount of base used per mole of the secondary amine (3) or (4) to be from 0.3 to 10 moles, and especially from 1 to 5 moles. An iodide such as sodium iodide, lithium iodide or tetrabutylammonium iodide, or a bromide such as sodium bromide, lithium bromide or tetrabutylammonium bromide, may be added as a catalyst to increase the reaction rate. When a catalyst is added, it is desirable for the amount of such addition to be from 0.001 to 2 moles, and especially from 0.005 to 0.5 mole, per mole of the secondary amine (3) or (4). To maximize the final yield, it is desirable to monitor the progress of the reaction using gas chromatography (GC) or thin-layer chromatography (TLC) until the reaction is complete. Generally, the reaction time is about 0.5 to 100 hours. Nitrogen heterocyclic compound (1) or (2) having the desired nitrogen-containing 5-membered ring structure and polar functional group is obtained by a conventional aqueous work-up from the reaction mixture. If necessary, compound (1) or (2) can be purified by an ordinary method such as distillation, chromatography or recrystallization. Alternatively, it may be possible to omit the aqueous work-up, either by using filtration to collect the salt that has formed in the reaction and subjecting the collected salt to purification, or by furnishing the reaction mixture directly to purification.

Resist compositions prepared using the nitrogen heterocyclic compounds having a nitrogen-bearing 5-membered ring structure and a polar functional group according to the invention are endowed with an excellent resolution and an excellent focus margin, and are thus useful in microfabrication using electron beams or deep-UV light. The addition of such compounds imparts significant effects in KrF resists, ArF resists, F₂ resists and EB resists. Such resists are highly suitable as micropatterning materials in the manufacture of VLSI chips.

EXAMPLES

Examples and comparative examples are given below by way of illustration, and not by way of limitation.

Resist Evaluation Examples:

In each example, a resist solution was prepared by dissolving a polymer, a photoacid generator, a base, a dissolution inhibitor and a crosslinking agent in a 70:30 by weight mixed solvent of propylene glycol monomethyl ether acetate (PGMEA) and ethyl lactate (EL), then filtering the solution using a Teflon® filter having a pore size of 0.1 μm.

The resulting resist solution was spin-coated onto a silicon wafer substrate on which had been formed a 55 nm thick film of DUV-30 (Nissan Chemical Industries, Ltd.) to hold the reflectance to KrF light (248 nm) to less than 1%, then baked at 100° C. for 90 seconds on a hot plate, giving a resist film having a thickness of 550 nm.

The resist film was exposed using an excimer laser stepper (NSR-S202A, manufactured by Nikon Corporation; NA=0.6; σ=0.75; 2/3 annular illumination) while varying the exposure dose and focus. Immediately after exposure, the resist was baked at 110° C. for 90 seconds, then developed for 60 seconds with a 2.38% solution of tetramethylammonium hydroxide in water, giving a resist pattern.

The resulting resist patterns were evaluated as described below. The results are shown in the following tables.

Method of Evaluation:

An optimal exposure dose (Eop) was the exposure which provided a 1:1 resolution of 0.16 μm lines and spaces. A focus margin was determined at the optimal exposure dose (Eop). The focus margin was defined as the absence of pattern film thickness loss and as having a size of not more than 0.16 μm±10%.

TABLE 1 Dissolution Photoacid inhibitor/ Focus Polymer generator Base crosslinker Sensitivity margin (pbw) (pbw) (pbw) (pbw) (mJ/cm²) (μm) Examples of invention Polymer5 PAG3 Amine1 — 30 0.8 (100) (2) (0.15) Polymer5 PAG3 Amine2 — 35 0.8 (100) (2) (0.18) Polymer5 PAG3 Amine3 — 31 0.9 (100) (2) (0.18) Polymer5 PAG3 Amine4 — 30 0.8 (100) (2) (0.18) Polymer5 PAG3 Amine8 — 29 0.9 (100) (2) (0.18) Polymer5 PAG3 Amine14 — 28 0.8 (100) (2) (0.18) Polymer5 PAG3 Amine16 — 32 0.8 (100) (2) (0.20) Polymer5 PAG3 Amine17 — 39 0.8 (100) (2) (0.18) Polymer5 PAG3 Amine23 — 38 0.8 (100) (2) (0.18) Polymer5 PAG3 Amine24 — 39 0.8 (100) (2) (0.16) Polymer5 PAG3 Amine25 — 41 0.9 (100) (2) (0.10) Polymer5 PAG3 Amine26 — 42 1.1 (100) (2) (0.09) Polymer5 PAG3 Amine27 — 39 1.0 (100) (2) (0.09) Polymer5 PAG3 Amine28 — 41 1.2 (100) (2) (0.08) Polymer5 PAG3 Amine29 — 40 0.9 (100) (2) (0.13) Polymer5 PAG3 Amine30 — 41 1.1 (100) (2) (0.13) Polymer5 PAG3 Amine33 — 40 1.0 (100) (2) (0.10) Polymer5 PAG3 Amine37 — 39 1.0 (100) (2) (0.13) Note that Amines 1 through 47 are amines of the structural formulas shown above.

TABLE 2 Dissolution Photoacid inhibitor/ Focus Polymer generator Base crosslinker Sensitivity margin (pbw) (pbw) (pbw) (pbw) (mJ/cm²) (μm) Examples of invention Polymer5 PAG3 Amine38 — 38 1.2 (100) (2) (0.15) Polymer5 PAG3 Amine42 — 41 1.0 (100) (2) (0.11) Polymer5 PAG3 Amine43 — 40 1.0 (100) (2) (0.13) Polymer5 PAG3 Amine44 — 37 1.1 (100) (2) (0.12) Polymer5 PAG3 Amine47 — 38 1.0 (100) (2) (0.13) Polymer1 PAG5 Amine37 — 45 0.9 (100) (2) (0.12) Polymer2 PAG5 Amine37 — 50 0.9 (100) (2) (0.12) Polymer3 PAG5 Amine37 — 48 1.1 (100) (2) (0.12) Polymer3 PAG4 Amine37 — 48 1.0 (100) (2) (0.12) Polymer4 PAG2 Amine37 Crosslinker 33 0.8 (100) (2) (0.12) (15) Polymer6 PAG1 Amine37 — 46 1.0 (100) (2) (0.12) Polymer7 PAG1 Amine37 — 48 1.0 (100) (2) (0.12) Polymer8 PAG1 Amine37 — 42 1.0 (100) (2) (0.12) Polymer9 PAG1 Amine37 — 40 0.8 (100) (2) (0.12) Polymer10 PAG1 Amine37 — 46 0.8 (100) (2) (0.12) Polymer11 PAG1 Amine37 — 43 1.0 (100) (2) (0.12) Polymer12 PAG4 Amine37 — 46 0.8 (100) (2) (0.12) Polymer13 PAG1 Amine37 — 47 0.8 (100) (2) (0.12) Polymer5 PAG2 Amine37 DRI 31 1.0 (100) (2) (0.12) (20)

TABLE 3 Dissolution Photoacid inhibitor/ Focus Polymer generator Base crosslinker Sensitivity margin (pbw) (pbw) (pbw) (pbw) (mJ/cm²) (μm) Comparative examples Polymer5 PAG2 — — 8 0.2 of invention (100) (2) Polymer5 PAG2 1,8-bis(dimethylamino)- — 35 0.4 (100) (2) naphthalene (0.2) Polymer5 PAG2 DBN — 34 0.4 (100) (2) (0.1) Polymer5 PAG2 DBU — 32 0.5 (100) (2) (0.1) Polymer1 PAG5 DBN — 52 0.2 (100) (2) (0.1) Polymer2 PAG5 DBN — 62 0.5 (100) (2) (0.1) Polymer3 PAG5 DBN — 51 0.3 (100) (2) (0.1) Polymer3 PAG4 DBN — 51 0.2 (100) (2) (0.1) Polymer4 PAG2 DBN Crosslinker 33 0.3 (100) (2) (0.1) (15) Polymer6 PAG1 DBN — 46 0.6 (100) (2) (0.1) Polymer7 PAG1 DBN — 48 0.6 (100) (2) (0.1) Polymer8 PAG1 DBN — 42 0.6 (100) (2) (0.1) Polymer9 PAG1 DBN — 45 0.4 (100) (2) (0.1) Polymer10 PAG1 DBN — 48 0.3 (100) (2) (0.1) Polymer11 PAG1 DBN — 42 0.4 (100) (2) (0.1) Polymer12 PAG4 DBN — 46 0.2 (100) (2) (0.1) Polymer13 PAG1 DBN — 45 0.3 (100) (2) (0.1) Polymer5 PAG2 DBN DRI1 29 0.3 (100) (2) (0.1) (20) 1,8-bis(dimethylamino)naphthalene

DBN: 1,5-diazabicyclo[4.3.0]-5-nonene

DBU: 1,8-diazabicyclo[5.4.0]-7-undecene 

1. A positive-working resist composition comprising: (A) a polar functional group-bearing nitrogen heterocyclic compound of the following general formula (1) or (2):

wherein A is a nitrogen atom or —C(R⁷)═B is a nitrogen atom or —C(R⁸)═R¹ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar function group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or a pair of R² and R³ and a pair of R⁴ and R⁵ may bond together to form a benzene, naphthalene or pyridine ring with the carbon atoms to which they are bonded; R⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms; R⁷ and R⁸ are each a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or R⁶ and R⁸ may bond together to form a benzene or naphthalene ring with the carbon atoms to which they are bonded; (B) an organic solvent; (C) a base resin having an acid labile group-protected acidic functional group which is alkali-insoluble or substantially alkali-insoluble, but becomes alkali-soluble when the acid-labile group is eliminated; and (D) a photoacid generator.
 2. The positive resist composition of claim 1 which further comprises (E) a dissolution inhibitor.
 3. A negative-working resist composition comprising: (A) a polar functional group-bearing nitrogen heterocyclic compound of the following general formula (1) or (2):

wherein A is a nitrogen atom or ≡C—R⁷; B is a nitrogen atom or ≡C—R⁸; R¹ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar function group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or a pair of R² and R³ and a pair of R⁴ and R⁵ may bond together to form a benzene, naphthalene or pyridine ring with the carbon atoms to which they are bonded; R⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms; R⁷ and R⁸ are each a hydrogen atom, a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms or an aryl group of 6 to 10 carbon atoms, or R⁶ and R⁸ may bond together to form a benzene or naphthalene ring with the carbon atoms to which they are bonded; (B) an organic solvent; (C′) a base resin which is alkali-soluble, but becomes substantially alkali-insoluble when crosslinked with acrosslinking agent; (D) a photoacid generator; and (F) a crosslinking agent which induces crosslinkage under the action of an acid.
 4. A patterning process comprising the steps of: (1) applying the positive resist composition of claim 1 onto a substrate; (2) heat treating the applied resist, then exposing the heat-treated resist through a photomask to high-energy radiation having a wavelength of at most 300 nm or an electron beam; and (3) heat treating the exposed resist, then developing the resist with a liquid developer.
 5. A patterning process comprising the steps of: (1) applying the negative resist composition of claim 3 onto a substrate; (2) heat treating the applied resist, then exposing the heat-treated resist through a photomask to high-energy radiation having a wavelength of at most 300 nm or an electron beam; and (3) heat treating the exposed resist, then developing the resist with a liquid developer. 